I don't know much about Odoo and haven't used v9 at all, so I can't speak from a totally informed position.
However I know that the guys looked at v9 originally and intentionally decided to build Odoo v8 instead. I don't recall the exact reasons but I do recall opinion that v8 was more community orientated and didn't push you so much towards paying. As v8 still receives updates (and they did all the hard the work) we were super pleased to add it to the library whether it was the latest version or not... Although perhaps we should name it "Odoo8" to make it clear?
It is still version 8
However I know that the guys looked at v9 originally and intentionally decided to build Odoo v8 instead. I don't recall the exact reasons but I do recall opinion that v8 was more community orientated and didn't push you so much towards paying. As v8 still receives updates (and they did all the hard the work) we were super pleased to add it to the library whether it was the latest version or not... Although perhaps we should name it "Odoo8" to make it clear?